Gas or vapor pump



Oct- 10, 1933 A. J. M. A. VAN DER Dol-:s DE BUE 1,930,403

GAS OR VAPOR PUMP Filed Aug. 13, 1932 Patented Oct. 10, 1933 UNITED STATES GAS 0R VAPOR PUMP Anne J. M. A. van der Does de Bije, The Hague,

' Netherlands Application August 13, 1932,.Seria.l No. 628,732, and in the Netherlands October 28, 1931 1 Claim.

Pumps are already known comprising intermeshing screws which are enclosed by a casing in such a manner that together and with the casing they form compartments adapted, on rotation of the screws, to move from the suction side towards the pressure side. In such arrangements various means are employed to ensure that the ilanks of the screw threads shall make a close t.

The invention relates to another arrangement for ensuring that the screws shall be satisfactorily sealed with respect to one another and to the casing. Moreover, the invention can be employed in order to obtain progressive compression in the compartments. This allows the pump to operate in an economical manner as a gas pump, since the said compression can be made to be approximately isothermal.

According to the invention, the pump is provided with a passage which extends from the pressure chamber of the pump to a closed compartment formed by the screws and the casing. The word passage must be taken to include a number of passages working in parallel, or a branched passage which opens into several consecutive compartments. The expression a cornpartment in this connection therefore does not mean one compartment.

The pump is prepared for operation by the pressure chamber being lled with so much liquid that the liquid under the action of the gas pressure ilows through the passage to the compartments. Preferably, passages are arranged in the bodies of the screws and provided with branch passages, the openings of which lie in the bottoms of the spaces between the screw threads. The liquid entering the compartments flows over the flanks of the screw thread and also to the outer circumference, so that a liquid seal, which is continually being renewed, is formed both between the screw threads, and between each thread and the casing. The screws therefore need not contact with one another or with the casing.

If the passages are made to open in various points longitudinally of the screws, and if the openings are properly dimensioned, the result can be obtained that during the movement of a compartment from the suction side towards the pressure side the volume of the mass of gas trapped in the compartment decreases owing to a greater amount of liquid being admitted than escapes by leakage. In these circumstances the gas is compressed during its movement towards the pressure side, and this compression may be approximately isothermal owing to cooling of (Cl. E30-143) the injected liquid, and/or to transference oi heat to a cooling jacket of the casing.

The suction chamber can readily be formed to collect the liquid, so that leaking liquid is trapped in the compartments with the gas or vapour and continuously returned to the pressure chamber.

In a pump according to the invention which is to be used as an air pump for a steam engine, the condensed water may be used as the liquid that is forced to the compartments. In @5 an air compressor the sealing liquid may, for example, be oil.

In the accompanying drawing two embodiments of the invention are illustrated by way of example.

In Fig. l (vertical section) and Fig. 2 (horizontal section), the casing 1 is provided with inlet branches 2, 3 and an outlet branch 4." Since this pump is intended to be an air pump for a condensation plant, the driving shaft 5 extends 75 through a stuing box of the outlet branch 4. The gear wheel 6 drives the pinions 7 and 8 of the screw shaft 9, 10.

'Ihe screws 11, 12, 13, 14 are secured to the shafts 9, 10 and their pitch is less than their diameter. The screw 1l is left handed and the screw 13 right handed. The Athreads of these two screws lit as closely as possible together and against the casing 1. The second pair l2, 14 is a duplicate of the pair 11, 13. It is clear that here the use of two pairs of screws has the object of balancing the axial forces.

Bored in the bodies of the screws are passages l5 and a number of branch passages 16, the openings of which lie in the bottoms of the gaps between the threads. The branches 16 are spaced so far from the suction chamber 17, 18 that they are connected with closed compartments only.

If the pressure chamber 19 is iilled with liquid to the level 20, the liquid will be forced into the passages 15 by the gas pressure and in the manner described above the screw threads are sealed with respect to one another and to the casing.

If, on account of leakages, such a large amount of liquid flows into the suction chambers 17, 18 as to reach the level 21, any further liquid entering is taken up by the compartments and automatically returned to the pressure chamber.

If it is not desired for the ends of the screws in the pressure chamber to be partly or wholly immersed in the liquid, the casing may be provided with a system of passages somewhat as shown in Fig. 3. The passage 22 opens at the bottom of the pressure chamber 19. The liquid forced therein flows through branches 23 into the compartments between the screw threads. The passages 22 may have a branch 24, whereby liquid can be forced to points at a higher level and ad- `iacent to the screws. If necessary, the liquid from these branch es may be sprayed against the bodies ofthe screws. The level 25 of the liquid in the pressure chamber may con- It has already been stated that the rst branch p 16 on the suction side opens into a closed compartment. In certain circumstances however, for example with a screw having only' few convolutions. it may be useful to inject the liquid before the compartment is entirely closed. In

that case the degree of lling will be somewhat i reduced.

What I claim is:-

In a gas or vapor pump, single threaded intermeshing screws having a pitch smaller than the diameter of the screws, a casing enclosing said screws, a compartment formed by said screws and said casing, a pressure chamber in said casing, and a passage arranged in the body of at least one of said screws, said passage opening into said4 compression chamber and into the gap between the threads of said screw immediately adjacent the front pressure face of the thread.

ANNE J. M. A. VAN nza DOES nl BIJE. 

